/*! \page Wannier_methodDoc Wannier method

Keyword: WANNIER

\section description Description

This method attempts to minimize the spread of the orbitals in periodic boundary conditions. It accomplishes this by maximizing the following value:
\f[
\sum_i |z_i|^2
\f]
where the sum is over all orbitals, and 
\f[
|z_i|^2=\sum_j {\left|\int{ \exp(-\vec{k_j}\cdot\vec{r}) \phi_i^2(\vec{r}) d\vec{r}\right|^2},
\f]
where the k's are the reciprocal lattice vectors.

The orbitals are optimized by rotating the orbitals:
\f[
{\boldsymbol \phi}'=M{\boldsymbol \phi}.
\f]
The matrix elements of M are allowed to be nonzero only between orbitals that are in the same ORB_GROUP.

\section options Options

\subsection reqopt Required 

<table>
<tr> <td> <b>Option</b> <td> <b>Type</b> <td> <b>Description</b>

<tr> <td> ORBITALS  <td> Section <td> A  \ref MO_matrixDoc section
<tr> <td> ORB_GROUP  <td> Section <td> The orbitals listed in this orbital group are allowed to mix. Can list multiple sections to define multiple mixing sectors.
</table>

\subsection optopt Optional

<table>
<tr> <td> <b>Option</b> <td> <b>Type</b> <td> <b> Default </b> 
     <td> <b>Description</b>
       <tr> <td> RESOLUTION <td> float <td> 0.2 <td> The pitch (in Bohrs) of the grid used for integration.
       <tr> <td> OUT_ORB <td> string <td> runid+.orb <td> Where the rotated orbitals will be stored.

</table>


*/
